Chapter 2 Matter and Energy Table of Contents Chapter 2 Matter and Energy Section 1 Explain transfer of energy; distinguish temperature & heat, convert.

Chapter 2 Matter and Energy

Table of Contents Chapter 2 Matter and Energy Section 1 Explain transfer of energy; distinguish temperature & heat, convert temperature scales, absolute zero, specific heat capacity Section 2 Scientific Method Section 3 Measurements and Calculations in Chemistry, Accuracy/Precision, sig figs; scientific notation

Objectives Explain that physical and chemical changes in matter involve transfers of energy. Apply the law of conservation of energy to analyze changes in matter. Distinguish between heat and temperature. Convert between the Celsius and Kelvin temperature scales. Section 1 Energy Chapter 2

Ex: You put your can of coke into the refrigerator so that you can get a cold can of coke. Why is it inaccurate to say that the fridge is cooling the coke? - Refrigerator Special see thru door

Measuring Temperature Temperature: measure of the average kinetic energy or energy of motion Use Celsius scale (but SI in Kelvin). Water freezes at 0ºC Water boils at 100ºC Body temperature 37ºC Room temperature 20 - 25ºC 0º C

Measuring Temperature Kelvin starts at absolute zero (-273º C) 1 K = 1ºC ºC = K - 273 K = ºC + 273 Kelvin is always bigger (good tip). Kelvin can never be negative. 273 K

Temperature and Temperature Scale Visual Concepts Chapter 2

The flow of energy -heat: Energy and heat: 1. Thermochemistry- concerned w/ the _____ _____ that occur during _______ ___. 2. Energy- capacity for _____ ___ or ________ _____ 3. Heat ( )- energy that transfers from one object to another due to temperature difference (ex. coke in a fridge)ex. coke in a fridge  only changes in heat can be detected!  flows from warmer  cooler object until objects have the same temperature  this energy that transfers is thermal energy  Joule (J) the SI unit of heat and energy heat changechemical rxn doing worksupplying heat q

Exothermic and Endothermic Processes Essentially all chemical reactions, and changes in physical state, involve either: release of heat (exothermic), or absorption of heat (endothermic)

Exothermic - heat flowing out of a system into its surroundings:  freezing  condensing  system loses heat as the surroundings heat up Ex. water freezing, raining, & CH 4 + 2O 2  CO 2 + 2H 2 O + Heat Endothermic - heat flowing into a system from its surroundings:  melting  boiling  system gains heat as the surroundings cool down Ex. ice melting, sweating, & CaCO 3 + heat  CaO + CO 2

C + O 2  CO 2 Energy ReactantsProducts  C + O 2 C O 2 395kJ + 395 kJ

CaCO 3  CaO + CO 2 Energy ReactantsProducts  CaCO 3 CaO + CO 2 176 kJ CaCO 3 + 176 kJ  CaO + CO 2

Conservation of Energy in a Chemical Reaction Section 1 Energy Chapter 2

Law of Conservation of Energy Visual Concepts Chapter 2

Heat, continued Transfer of Heat May Not Affect the Temperature The transfer of energy as heat does not always result in a change of temperature. For example, consider what happens when energy is transferred to a mixture of ice and water. As energy is transferred as heat to the ice-water mixture, the ice cubes will start to melt. The temperature of the mixture remains at 0°C until all of the ice has melted. Section 1 Energy Chapter 2

Heat, continued Transfer of Heat May Not Affect the Temperature, continued Once all the ice has melted, the temperature of the water will start to increase until it reaches 100°C. As the water boils, the temperature remains at 100°C until all the water has turned into a gas. The temperature remains constant during the physical changes in this system. Section 1 Energy Chapter 2

Heating Curve for Water Section 1 Energy Chapter 2

Heat Capacity Heat Capacity: the amount of heat needed to increase the temperature of an object exactly 1 o C Heat Capacity of a substance depends on two factors: 1) A 20 g iron bar and 20 g of water (both at room temp) are set outside on a sunny day for 20 minutes. After the 20 minutes elapse which will have a higher temperature? 2) Two cups of room temp water are set outside on a sunny day for 1 hour. Cup A: 20 g of water Cup B: 200 g of water Which will be warmer after the one hour? Ans:Fe Factor 1: Chemical Structure Ans: Cup A Factor 2: Mass

the amount of heat it takes to raise the temperature of 1 gram of the substance by 1 o C specific heat capacity ( C p )- the amount of heat it takes to raise the temperature of 1 gram of the substance by 1 o C at constant pressure  also called “Specific Heat” cal/g°CJ/g°C (or J/gK) water 1.00 4.18 aluminum0.22 0.90 copper0.093 0.39 silver0.057 0.24 gold0.031 0.13

Specific Heat Capacity Visual Concepts Chapter 2

To solve for heat capacity (q)… To calculate, use the formula: “q” is heat, unit- J or cal “m” is mass, unit- g “  T” = change in temperature, (  T = T f -T i ) unit- o C or K “C p ”or “C”= Specific Heat Capacity units: J/(g o C) or cal/(g o C) q = mC p T q = mC p T

Same eq’n, different look! q = m Cp  T q = m · Cp ·  T C p = C p =  T =  T = (  T = T f -T i ) m = m = q m ·  T q m Cp m · Cp q Cp Cp · TCp Cp · T

Example Problems 1. It takes 24.3 calories to heat 15.4 g of a metal from 22 ºC to 33ºC. What is the specific heat of the metal? given: q = 24.3 cal m = 15.4 g  T = T f -T i =33 – 22 = 11ºC Cp = ?? q = m Cp  T Cp = = = q m  T (24.3 cal) (15.4 g)(11 ºC) 0.14 cal/(g o C)

Try Practice problems on pg 61:

Demo: Burning Water Predict why the water appears to have caught on fire. Does water burn? What liquids do you know burn? Of the liquids named above, which liquids are less dense than water? When fighting a fire created by gasoline burning, is it wise to try to get the fire out with water from a fire hose? Why not? What should be used instead?

Objectives Describe how chemists use the scientific method. Explain the purpose of controlling the conditions of an experiment. Explain the difference between a hypothesis, a theory, and a law. Section 2 Studying Matter and Energy Chapter 2

How Did Jack and Jill Die?  Objective: To learn what a variable is and to practice identifying it  Directions: Listen to the scenario Discuss with your group the possible variables Change variables to solve the crime Ask me, “If _____ would Jack and Jill be alive?” (ex. If the window is shut, would the plant have fallen to the ground?)

You are the detective. You walk into the crime scene. You are careful not to tamper with any of the evidence. Here is what you observe:

Jack and Jill are dead. They are lying on the carpet. There is shattered glass around them. The floor is wet. You look around and see a cat going in and out of the room thru the open window.

You ask yourself, “Was it a burglary?” You look around the room for stolen objects. Everything seems to be in place. You observe Jack and Jill. They are cold. You don’t see any blood and there are no outer scars or bruises. So how did they die?

How Did Jack and Jill Die?  Objective: To learn what a variable is and to practice identifying it  Directions: Listen to the scenario Discuss with your group the possible variables Change variables to solve the crime Ask me, “If _____ would Jack and Jill be alive?” (ex. If the window is shut, would the plant have fallen to the ground?)

The Scientific Method The scientific method is a series of steps followed to solve problems, including collecting data (asking questions) formulating a hypothesis testing the hypothesis stating conclusions A scientist chooses which set of steps to use depending on the nature of the investigation. Section 2 Studying Matter and Energy Chapter 2

Scientific Method Visual Concepts Chapter 2

Scientific Method Section 2 Studying Matter and Energy Chapter 2

The Scientific Method, continued Teflon Was Discovered by Chance In 1938, DuPont chemist Dr. Roy Plunkett, was trying to produce a new coolant gas to use as a refrigerant. He wanted to react a gas called tetrafluoroethene (TFE) with hydrochloric acid. He recorded the mass of a cylinder of TFE. He then opened the cylinder to let the TFE flow into a container filled with hydrochloric acid, but no TFE came out of the cylinder. Section 2 Studying Matter and Energy Chapter 2

The Scientific Method, continued Teflon Was Discovered by Chance, continued Because the cylinder had the same mass as it did when it was filled with TFE, Plunkett knew that none of the TFE had leaked out. When he opened it, he found only a few white flakes. Plunkett analyze the white flakes and discovered that the TFE molecules joined together to form a long chain of polytetrafluoroethene (PTFE). These long-chained molecules were very slippery. Section 2 Studying Matter and Energy Chapter 2

Comparing Theories and Laws Visual Concepts Chapter 2

Scientific Explanations, continued Theories and Laws Have Different Purposes, continued For example, the law of conservation of mass states that the products of a chemical reaction have the same mass as the reactants have. This law does not explain why matter in chemical reactions behaves this way; the law simply describes this behavior. Keep in mind that a hypothesis predicts an event, a theory explains it, and a law describes it. Section 2 Studying Matter and Energy Chapter 2

Models Visual Concepts Chapter 2

Test Prep: In order to advance to the level of a theory, a hypothesis should be 1. obviously accepted by most people. 2. a fully functional experiment. 3. in alignment with past theories. 4. repeatedly confirmed by experimentation.

Matter is made of atoms that have positive centers of neutrons and protons surrounded by a cloud of negatively charged electrons. This statement is 1. a theory. 2. a hypothesis. 3. an inference. 4. an observation.

Objectives Distinguish between accuracy and precision in measurements. Determine the number of significant figures in a measurement, and apply rules for significant figures in calculations. Calculate changes in energy using the equation for specific heat, and round the results to the correct number of significant figures. Chapter 2 Section 3 Measurements and Calculations in Chemistry

Uncertainty in Measurement 1. Accuracy, Precision, Error: a. Accuracy: b. Precision: c. Accepted Value: ______ ____ based on reliable resources d. Experimental Value: value _________ in the lab e. Uncertainty -= Error = _______ value - _____ value 2. Significant Figures in Measurement: a. Sig. fig.: all digits that are known plus one ________ digit b. Addition/Subtraction- round to the least ______ place c. Multiplication/Division- round to the least _______ d. Round off to the correct sig fig at __________. measure of how close the measurement comes to the true value how close a repeated measurement is to one another correct value measured accepted exp’t estimated precise sig. fig. the very end

Visual Concepts Accuracy and Precision Chapter 2

Significant Figures http://www.extrem-sport.com/bodybuilding.htmhttp://www.sf-film.dk/austinpowers/index_dvd_features.htm

Visual Concepts Significant Figures Chapter 2

Significant Figures, continued Exact Values Have Unlimited Significant Figures Some values have an unlimited number of significant figures. These exact values have no uncertainty. One type of exact value, a count value, is determined by counting, not by measuring. Another value that can have an unlimited number of significant figures is a conversion factor. Ignore both count values and conversion factors when determining the number of significant figures. Section 3 Measurements and Calculations in Chemistry Chapter 2

B. Introduction: When making measurements or doing calculation you should not keep more digits in a number than is ________. These rules of significant figures will show you how to determine the correct number of digits. C. What is a significant figure? Significant figures in a measurement are all values (digits) known precisely, plus ______ digit that is estimated. Example: Make the measurement with the correct significant figures. 1. ___________ _ 2. ___________ _ 3. ____________ _ 4. ____________ _ 5. ____________ _ 6. ___________ _ 7. ___________ _ 8. ___________ _ 1. 2.2. 3. 4.4. 5.6. 7. 8. 9 cm 10 cm 9 cm 10 cm 9 cm 10 cm 0 cm 1 cm justified one 9.24 cm 9.88 cm 9.00 cm 9.70 cm 9.0 cm 9.8 cm 0.02 cm 0.90 cm

D.How do you determine sig figs in a measurement that has already been recorded? Sig Figs: The Rules 1. Every nonzero digit in a recorded measurement is significant. Examples:47,3575 sig figs 25________ 2.Zeros between nonzero digits are significant. (“Sandwich rule”) Examples: 1,007 4 sig figs 305 _______ 2 3 3. Zeros in front of all nonzero digit are not significant. Examples: 0.00238 3 sig figs 0.98 ______ 0.000006 ______ 2 1

4.Zeros at the end of a number and to the right of a decimal point are significant. Examples:426.005 sig figs 2.060______ 0.8080______ 4 4 5. Zeros at the end of a measurement where there is no decimal point are NOT significant. Examples:560002 sig figs 30001 sig fig 240804 sig figs 110100 4 sig figs

How many significant figures are in each of the following measurements? 24 mL2 significant figures 3001 g 4 significant figures 0.0320 m 3 3 significant figures 6.4 x 10 4 molecules 2 significant figures 560 kg2 significant figures

Practice: 1. Determine the number of significant figures for each of the following measurement. (a) 54320.0 (b) 0.004550(c) 151309 (d) 10.54 (e) 5.20 x 10 5 (f) 15,000(g) 10.04 (h) 0.0750 2.When completing calculations, it is often necessary to round the final answer to a particular number of significant figures (round up for 5 and above; keep digits the same for 4 and below). Round the above measurements to 2 significant figures.Example: 0.0753= 0.075 107.0 = _______________ 54000 5.4 x 10 4 6 0.0046 4.6 x 10 –3 4 150,000 1.5 x 10 5 6 11 4 5.2 x 10 5 3 1.5 x 10 4 2 10. 1.0 x 10 1 4 0.075 7.5 x 10 –2 3 110 or 1.1 x 10 2

3. Determine the number of sig figs for each measurement. Round the measurements to 2 sig figs. If original measurement only contains 1 or 2 sig figs, leave the second line blank. # sig figs Rounded Answer 1. 0.0037_____________________ 2. 134.1_____________________ 3. 1,000,000_____________________ 4. 5.730 x 10 2 _____________________ 5. 410.50_____________________ 6. 79500_____________________ 7. 3071.04_____________________ 8. 4.08 x 10 -6 _____________________ 9. 0.998_____________________ 10. 1.570_____________________ 2 1 4 5 3 6 3 3 4 130 = 1.3 x 10 2 1.0 x 10 6 5.7 x 10 2 = 4.1 x 10 2 8.0 x 10 4 = 3.1 x 10 3 4.1 x 10 -6 1.0 1.6 ------------- 410 3100 4

Practice cont.: 11. 14.04_____________________ 12. 5.401_____________________ 13. 1340_____________________ 14. 0.00566_____________________ 15. 0.8120_____________________ 16. 18.009_____________________ 17. 100.5_____________________ 18. 3008_____________________ 19. 112040.0_____________________ 20. 43.05_____________________ # sig figs Rounded Answer 4 4 3 3 4 5 4 4 7 4 = 1.3 x 10 3 1300 14 5.4.0057 = 5.7 x 10 -3 0.81 18 1.0 x 10 2 3.0 x 10 3 110 000 = 1.1 x 10 5 43

Example: 12.11 m + 8.0 m + 1.013 m = 21.123 (Rounds to ONE place after the decimal) = 21.1 m (1) 21 cm – 18.3 cm = Rules for Significant Figure in Calculations Multiplication or Division: The number of sig figs in the result is the same number as the number in the least precise (least sig figs) measurement. Example: (1) 4.56 m x 1.4 m = 6.38 m 2 (Round to TWO sig figs) = 6.4 m 2 (a) 17.24 x 0.52(b) 118.24 x 3.5(c) Addition or Subtraction: The result has the same number of decimal places as the least precise measurement used in the calculation. (2) 10000.00 mm + 25.116 mm = 10025.12 mm3 cm 8.9648 9.0 413.84 1.913034301 4.1 x 10 2 1.91

Significant Figures Multiplication or Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x 3.6666 = 16.536366= 16.5 3 sig figsround to 3 sig figs 6.8 ÷ 112.04 = 0.0606926 2 sig figsround to 2 sig figs = 0.061

Significant Figures Addition or Subtraction The answer cannot have more digits to the right of the decimal point than any of the original numbers. 89.332 1.1+ 90.432 round off to 90.4 one significant figure after decimal point 3.70 -2.9133 0.7867 two significant figures after decimal point round off to 0.79

Significant Figures 1. Calculate the area of the dark rectangle. 122.973 123 123 cm 2 2. Calculate the volume of the object 6 6.14865 6 cm 3 h = 0.05 cm l = 17.9 cm w = 6.87 cm

Significant Figures 3. Calculate the sum of the length, width, and height. 24.82 24.8 24.8 cm 4. What is the length of each segment? A = 10.07 cm C = 10.50 cm D = 11.00 cm B = 10.23 cm 11 cm10 cm ABCD

Scientific Notation, continued Scientific Notation with Significant Figures 1.Use scientific notation to eliminate all place-holding zeros. (esp. #’s too large or too small or to control sig figs) Section 3 Measurements and Calculations in Chemistry Chapter 2

Exponential Notation (_________ Notation)Exponential Notation A. Chemistry examples: 1. Avogadro’s Number 2. Mass of an electron Scientific 6020000000000000000000006.02 x 10 23 0.000000000000000000000000000000911 Kg 9.11 x 10 -31 Kg B. Technique to change from positional notation to scientific notation: 1. Leave ___ number to the ______ of the decimal. 2. When the decimal is moved to the ______, the exponent is ____________. 3. When the decimal is moved to the ______, the exponent is ____________. 4. Number must contain the same number of ____________ as the original value. Sig figs (S.F.) right (+) positive left 1 (-) negative

Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000,000 6.022 x 10 23 The mass of a single carbon atom in grams: 0.0000000000000000000000199 1.99 x 10 -23 N x 10 n N is a number between 1 and 10 n is a positive or negative integer

Scientific Notation 568.762 n > 0 568.762 = 5.68762 x 10 2 move decimal left 0.00000772 n < 0 0.00000772 = 7.72 x 10 -6 move decimal right Addition or Subtraction 1.Write each quantity with the same exponent n 2.Combine N 1 and N 2 3.The exponent, n, remains the same 4.31 x 10 4 + 3.9 x 10 3 = 4.31 x 10 4 + 0.39 x 10 4 = 4.70 x 10 4

Scientific Notation Multiplication 1.Multiply N 1 and N 2 2.Add exponents n 1 and n 2 (4.0 x 10 -5 ) x (7.0 x 10 3 ) = (4.0 x 7.0) x (10 -5+3 ) = 28 x 10 -2 = 2.8 x 10 -1 Division 1.Divide N 1 and N 2 2.Subtract exponents n 1 and n 2 8.5 x 10 4 ÷ 5.0 x 10 9 = (8.5 ÷ 5.0) x 10 4-9 = 1.7 x 10 -5 http://micro.magnet.fsu.edu/primer/java/scien ceopticsu/powersof10/

Convert the following to scientific notation: 1. 135000(3 s.f)____________ 2. 0.005500____________ 3. 120,000,000,000 (2 s.f.)____________ 4. 0.00000004441____________ 4.441 x 10 -8 1.2 x 10 11 5.500 x 10 -3 1.35 x 10 5 Use of calculator with scientific notation: Step 1: Enter the number Step 2: Press the Expontent button ____ or ____ Step 3: Enter the exponent Step 4: If negative exponent, use ____ key. +/-1.61 -19 1.61 19 1.61 00EXPEE 1.61 1.61 x 10 -19

Exponent problems (Use correct sig figs!) = 1.2 x 10 33 = 1 x 10 -27 Raising to a powerTaking a rootStep 1: Enter numberStep 2: Press Step 3: Enter powerStep 3: Enter rootStep 4: PressExample: xyxy xyxy 2 nd = = (a) (14.5) 6 = (b) (1.72 x 10 5 ) 4 = 9.29 x 10 6 8.75 x 10 20 2.26 0.0528

1.Which of the following determines the temperature of a substance? A.charge on ions B.color C.motion of particles D.total mass of material Standardized Test Preparation Understanding Concepts Chapter 2

2.Which of these processes is an endothermic physical change? F.an explosion G.melting of butter H.condensation of a gas I.formation of a solid when two liquids are mixed Standardized Test Preparation Understanding Concepts Chapter 2

3.Which of the following definitely indicates an error in an experiment? A.hypothesis not supported B.results contradict a theory C.unexpected results D.violation of a scientific law Standardized Test Preparation Understanding Concepts Chapter 2

4.Every chemical change involves F.the formation of a different substance. G.the vaporization of a liquid. H.separation of states of matter. I.the release of energy. Standardized Test Preparation Understanding Concepts Chapter 2

5.Use the concept of specific heat to analyze the following observation: two pieces of metal with exactly the same mass are placed on a surface in bright sunlight. The temperature of the first block increases by 3°C while the temperature of the second increases by 8°C. Standardized Test Preparation Understanding Concepts Chapter 2

5.Use the concept of specific heat to analyze the following observation: two pieces of metal with exactly the same mass are placed on a surface in bright sunlight. The temperature of the first block increases by 3°C while the temperature of the second increases by 8°C. Answer: Because the temperatures of the objects differ under the same conditions, they must have different specific heats, so they are made of different metals. Standardized Test Preparation Understanding Concepts Chapter 2

6.Describe the scientific method. Standardized Test Preparation Understanding Concepts Chapter 2

6.Describe the scientific method. Answer: The scientific method is a series of steps followed to solve problems, including collecting data, formulating a hypothesis, testing a hypothesis, and stating conclusions. Standardized Test Preparation Understanding Concepts Chapter 2

Several tests are needed before a new drug is approved for treatment. First, laboratory tests show the drug may be effective, but it is not given to humans. Next, human subjects receive the drug to determine if it is effective and if it has harmful side effects. Later “double-blind” tests are performed, where some patients receive the drug and others receive something that looks the same without the drug. Neither patient nor researcher knows who receives the drug. The double-blind test avoids introducing bias into the results based on expectations of the drug’s effectiveness. After testing, results are published to allow other researchers to evaluate the process and review the conclusions. These reviewers are important because they can provide independent analysis of the conclusions. Standardized Test Preparation Reading Skills Chapter 2

7.Which of the following is a reason that it is important that scientific results be confirmed by independent researchers? A.to introduce bias into expected results B.to obtain additional research funding C.to verify results are reproducible when conditions are duplicated D.to introduce changes into the experiment and determine whether the result changes Standardized Test Preparation Reading Skills Chapter 2

8.Why is it necessary for the investigator to accurately report experimental conditions? F.to guarantee that the right person receives credit for the discovery G.to show that researchers knew how to follow the scientific process H.to prove that the experiment was actually performed and not made up I.to allow other scientists to reproduce the experiment and confirm the observations Standardized Test Preparation Reading Skills Chapter 2

Use the graph below to answer questions 9–12. Standardized Test Preparation Interpreting Graphics Chapter 2

9.What is happening during the portion of the graph labeled Heat of Vaporization, in which temperature does not change? A.No energy is added to the water. B.Added energy causes water molecules to move closer together. C.Added energy causes the water molecules to move farther apart. D.Added energy causes the water molecules to change from the solid state to the gas state. Standardized Test Preparation Interpreting Graphics Chapter 2

10.For a given mass of water, which of these processes requires the greatest addition of energy for a 1°C temperature change F.heating a gas G.heating a solid H.heating a liquid I.changing a solid to a liquid Standardized Test Preparation Interpreting Graphics Chapter 2

11.How does the temperature change between the beginning of vaporization and the end of vaporization of water? A.temperature decreases slowly B.temperature does not change C.temperature increases slowly D.temperature increases rapidly Standardized Test Preparation Interpreting Graphics Chapter 2

12.On what portion of this graph are water molecules separated by the greatest distance? Standardized Test Preparation Interpreting Graphics Chapter 2

12.On what portion of this graph are water molecules separated by the greatest distance? Answer: The right side of the graph, which shows the conditions of water in the gas phase. Standardized Test Preparation Interpreting Graphics Chapter 2

Chapter 2 Matter and Energy Table of Contents Chapter 2 Matter and Energy Section 1 Explain transfer of energy; distinguish temperature & heat, convert.

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Chapter 2 Matter and Energy Table of Contents Chapter 2 Matter and Energy Section 1 Explain transfer of energy; distinguish temperature & heat, convert.

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